The invention relates to a shaping apparatus for the shaping of plastics material pre-forms into plastics material containers with a plurality of blow moulding stations and with at least one control device for the control of blow moulding pressures and/or volume flows at the blow moulding stations, in which the at least one control device comprises at least one control valve with a control piston part which is guided in a cylinder part and by means of which a cross-section of a blow moulding air duct is capable of being closed.
A generic shaping apparatus of this type is known for example from the Laid-Open Specification DE 10 2010 052 903 A1, in which is provided a control device for controlling a blow moulding pressure which has a control piston guided in a cylinder. The control piston can be moved in the direction of the longitudinal axis thereof by means of a pneumatic control pressure in order to close, in particular, a main flow path for the flow of blow moulding air.
A generic shaping apparatus with blow moulding stations arranged on a rotating blow moulding wheel for the blow moulding of containers from a thermoplastic material is likewise known from the patent specification EP 1 271 029 B1. This shaping apparatus comprises, in addition, a device for the pneumatic control of a blow moulding pressure, the device having a control piston which is guided in a cylinder and which can be displaced by means of a pneumatic control pressure in the direction of the longitudinal axis of the piston in such a way that, in particular, a main flow path for guiding blow moulding air is capable of being closed.
A drawback of known shaping apparatus of this type is that a change in position of the respective control piston for closing, and also for opening, a main flow path for the supply of blow moulding compressed air usually only takes place in a relatively undifferentiated manner. In particular, an unsatisfactory scatter of the valve switching times of up to +/−2 ms frequently occurs on account of the design, as a result of which the quality of the actual shaping process can be adversely affected.
It would be desirable to overcome at least the drawback named above on generic shaping apparatus.